Magnetic disk device and magnetic head slider

ABSTRACT

A magnetic disk device, which is provided with a magnetic head slider mounted with a magnetic head and a magnetic disk, and of which the magnetic head slider has the possibility of contacting the magnetic disk at the vicinity of the magnetic head,  
     wherein the magnetic head slider has the size of 1.25 mm or less in length, 1 mm or less in width and 0.3 mm or less in thickness, and the friction force exerted between the magnetic head slider and the magnetic disk is 10 mN or less.  
     The magnetic head comprises four substantially parallel surfaces and the depth from a first surface which is the most adjacent surface to the magnetic disk to a second surface is 10 nm to 50 nm, the depth from the second surface to a third surface is 50 nm to 200 nm, and the depth from the third surface to a fourth surface is 400 nm to 1  m.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a magnetic disk device, particularly tothe structure of a magnetic head slider and a magnetic disk in a contactrecording magnetic disk device in which the magnetic head slider touchesthe magnetic disk.

[0002] To increase the recording density of the magnetic disk device,the narrowing of flying height, that is defined as the spacing between amagnetic head slider mounted with a magnetic head and a rotatingmagnetic disk, is important.

[0003] The uniform flying height over the all surface of the magneticdisk is also required. Further, the fluctuation of flying height by anenvironmental variation, especially the decrease of flying height by thedrop of atmospheric pressure in the high altitude is required to beminimized.

[0004] In proportion to the decrease of the flying height, thepossibility of the contact of the magnetic head slider with the magneticdisk increases, and if the contacting state is severe, the magnetic headslider crashes against the magnetic disk and there is the possibility ofdestroying the recorded data on the magnetic disk.

[0005] As a conventional technology for generally equalizing the flyingheight over the all surface of the magnetic disk, reducing the decreaseof flying height and keeping the uniform flying height all over themagnetic disk in the high altitude, a technology is disclosed byJP-A-2000-57724.

[0006] Said Japanese publication discloses a step air bearingsub-ambient pressure force magnetic head slider which generallyequalizes the flying height over the all surface of the magnetic diskand enabling to reduce the decrease of the flying height in the highaltitude by the adequate combination of a step air bearing having therecess of the depth of sub-microns, the recess deeper than that of theair bearing for generating sub-ambient pressure force and the railsurfaces.

SUMMARY OF THE INVENTION

[0007] A first thing to do to increase the recording density of magneticdisk device while keeping the high reliability of it is to devise themeasures of preventing the contact between the magnetic head slider andthe magnetic disk by narrowing and equalizing the flying height over theall surface of the magnetic disk, reducing the fluctuation of the flyingheight caused by the variation of the manufacturing of the magnetic headslider, reducing the fluctuation of flying height by seek operations,and reducing the decrease of flying height in the high altitude.

[0008] However, whatever measures are taken with above describedeffects, the contact between the magnetic head slider and the magneticdisk is unavoidable with the narrow flying height of 15 nm or less andthe vibration or the wear of the magnetic head slider are becoming a newproblem.

[0009] Regarding to the step air bearing sub-ambient pressure forcemagnetic head slider disclosed by said JP-A-2000-57724, it is disclosedthat the flying height is generally uniform, and the fluctuations of theflying height by the variation of the manufacturing, seek operations andin the high altitude can be reduced.

[0010] However, it gives no considerations especially to the vibrationof magnetic head slider caused by the contact with the magnetic disk andimprovement on this point has been requested.

[0011] The present invention relates to the above described needs andintends to provide the magnetic disk device and the magnetic head sliderthat are generally uniform with the flying height over the all surfaceof the magnetic disk, reduced with the fluctuations of flying height bythe variation of the manufacturing, seek operations and in the highaltitude, and in case of the contact between the magnetic head sliderand the magnetic disk, the magnetic head slider slides on the surface ofthe magnetic disk smoothly maintaining a high reliability.

[0012] To solve above described problems, the present invention adoptsthe following constitution.

[0013] A magnetic head slider comprising a magnetic head mountingsurface on the air flow-out side which is the closest to the magneticdisk in operation and mounted with the magnetic head, a slider railsurface which is separated from said magnetic head mounting surface andformed with the surface near to air flow-in side and both side surfacesnear the air flow-in edge having the depth of 10 nm to 50 nm from themagnetic head mounted surface, a slider step air bearing surface formedsurrounding said slider rail surface and has the depth of 50 nm to 200nm from said slider rail surface, and a recess for generatingsub-ambient pressure force surrounding said slider step air bearingsurface and having the depth of 400 nm to 1.3 μm from said slider stepair bearing surface.

[0014] A magnetic disk device is provided with the magnetic head slidermounted with the magnetic head and the magnetic disk that is a datarecording medium, wherein the vicinity of said magnetic head of saidmagnetic head slider has the possibility of contacting said magneticdisk, said magnetic head slider has the length of 1.25 mm or less, thewidth of 1 mm or less and the thickness of 0.3 mm or less, and thefriction force exerted between said magnetic head slider and saidmagnetic disk is 10 mN or less.

[0015] A magnetic disk device is provided with the magnetic head sliderhaving the magnetic head and the magnetic disk that is the datarecording medium, wherein the vicinity of said magnetic head of saidmagnetic head slider has the possibility of contacting said magneticdisk, the floating pitch angle of said magnetic head slider is 50micro-radian or more, the mean surface roughness Ra of said magneticdisk is 2 nm or less and the peak count of it is 700/400 μm2 or more.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is the top view of the magnetic head slider of the firstpreferred embodiment of the present invention.

[0017]FIG. 2 is the figure showing the A-A cross section in thedirection of arrows in the FIG. 1.

[0018]FIG. 3 is the figure illustrating the contacting state between themagnetic head slider and the magnetic disk facing therewith in the firstpreferred embodiment of the present invention.

[0019]FIG. 4 is a diagram showing the relation between the frictionforce generated by the contact between the magnetic head slider and themagnetic disk, and the amplitude of vibration in the first preferredembodiment of the present invention.

[0020]FIG. 5 is a diagram showing the relation between the pitchattitude angle of the magnetic head slider and the amplitude ofvibration in the first preferred embodiment of the present invention.

[0021]FIG. 6 is a diagram showing the relation between the peak count ofthe magnetic disk and the amplitude of vibration of the magnetic headslider of the first preferred embodiment of the present invention.

[0022]FIG. 7 is a diagram showing the floating profiles of the magnetichead slider of the first preferred embodiment of the present inventionin the ground altitude and the high altitude.

[0023]FIG. 8 is a diagram showing the relation between the depth d1between a first surface constituting element and a second surfaceconstituting element of the magnetic head slider of the first preferredembodiment of the present invention, and the amplitude of vibration.

[0024]FIG. 9 is a diagram showing the relation between the depth d2between a second surface constituting element and a third surfaceconstituting element of the magnetic head of the first preferredembodiment of the present invention, and the ratio of flying heights.

[0025]FIG. 10 is a diagram showing relation between the depth 3 betweenthe third surface constituting element and the fourth surfaceconstituting element of the magnetic head slider of the first preferredembodiment of the present invention, and the difference of flyingheights in the ground altitude and the high altitude.

[0026]FIG. 11 is a diagram showing the relation between the area of thefirst surface constituting element 5 a of the magnetic head slider ofthe first preferred embodiment of the present invention, and theamplitude of vibration.

[0027]FIG. 12 is drawings illustrating an example of the process ofproducing a magnetic head slider of the first preferred embodiment ofthe present invention.

[0028]FIG. 13 is a drawing showing the top view of the magnetic headslider of the second preferred embodiment of the present invention.

[0029]FIG. 14 is a drawing showing A-A cross section in the direction ofarrows in the FIG. 13.

[0030]FIG. 15 is a drawing showing the top view of the magnetic headslide of the third preferred embodiment of the present invention.

[0031]FIG. 16 is a drawing showing the top view of the magnetic headslider of the fourth preferred embodiment of the present invention.

[0032]FIG. 17 is a drawing showing the top view of the magnetic headslider of the fifth preferred embodiment of the present invention.

[0033]FIG. 18 is a figure illustrating a magnetic disk device mountedwith a load/unload mechanism provided with the magnetic head slider ofthe present invention.

[0034]FIG. 19 is a drawing showing the top view of the magnetic headslider of the sixth preferred embodiment of the present invention.

[0035]FIG. 20 is a drawing showing the top view of the magnetic headslider of the seventh preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Following is the description of the magnetic head slider and themagnetic disk device therewith of the preferred embodiment of thepresent invention referring to drawings.

[0037]FIG. 1 is a top view of the magnetic head slider of the firstpreferred embodiment of the present invention. FIG. 2 is the A-A crosssection in the direction of arrows in FIG. 1.

[0038] As is shown by a figure, the magnetic head slider 1 of the firstpreferred embodiment of the present invention constitutes provided withan air flow-in edge 2, an air flow-out edge 3 and a floating surface 4.

[0039] Said floating surface 4, facing a magnetic disk which is notshown, is provided with first surface constituting elements 5 a, 5 b and5 c, which form the first surface most adjacently positioned to themagnetic disk, second surface constituting elements 6 a, 6 b and 6 c,which form the second surface more separated from the magnetic disk thanthe first surface, third surface constituting elements 7 a, 7 b and 7 c,which form the third surface more separated from the magnetic head thanthe second surface, and fourth surface constituting elements 8 whichforms the fourth surface most separated from the magnetic disk.

[0040] The first to the fourth surfaces are substantially parallel, thedepth d1 from the first surface constituting element 5 a to the secondsurface constituting element 6 a is 30 nm, the depth d2 from the secondsurface constituting element 6 a to the third surface constitutingelement 7 a is 120 nm and the depth from the third surface constitutingelement 7 a to the fourth surface constituting element 8 is 800 nm.

[0041] The magnetic head slider 1 has the length of 1.25 mm, the widthof 1.0 mm and the thickness of 0.3 mm. The first surface constitutingelement 5 a is provided with a magnetic head 9.

[0042] The magnetic head 9 comprises a recording inductive head and areproducing GMR (Giant Magneto-Resistance) head.

[0043] The recording gap of the inductive head and the reproducing gapof GMR are formed on a surface which is substantially the same surfacewith the first surface constituting element 5 a.

[0044] The gap means either the recording gap or the reproducing gaphereafter.

[0045] Here, the substantially same surface means that, as the hardnessis different among the base material (generally AlTiC) constituting themagnetic head slider 1, the constituting member of the magnetic head 9and the protecting member (generally alumina) of the magnetic head, thesofter magnetic head is more abraded in lapping work forming thedifference in level of several nano-meters. This difference of the levelis not intentionally formed and clearly different from the othersurfaces that are intentionally formed.

[0046] In this preferred embodiment of the invention, a surface providedwith the magnetic head 9 is defined as the first surface but aprotruding surface for the purpose of preventing sticking at the contactstop of the magnetic head on the magnetic disk can be formed on thecloser side to the magnetic disk than the first surface.

[0047]FIG. 3 is a figure illustrating the relative positions of amagnetic head slider 1 and a magnetic disk 10 of the above-describedfirst preferred embodiment of the present invention operating inside themagnetic disk device.

[0048] When airflow generated by the rotation of the magnetic disk 10enters between the magnetic head slider 1 and the magnetic disk 10,pressure is generated between the second surface constituting elements 6a, 6 b and 6 c, and the magnetic disk 10, then the magnetic head slider1 begins to float being taken off from the magnetic disk 10.

[0049] In this preferred embodiment of the present invention, the secondsurface constituting elements 6 a, 6 b and 6 c correspond to the railsurfaces of the conventional magnetic head slider having been widelyused.

[0050] The magnetic head slider 1 is generally designed to float in suchattitude that the flying height on the side of the air flow-in edge 2 islarger than the flying height on the side of the air flow-out edge.Therefore, the air flow-out edge side approaches most adjacently to themagnetic disk 10.

[0051] In the magnetic head slider of the first preferred embodiment ofthe present invention, the first surface constituting element 5 aapproaches most adjacently to the magnetic disk 10 and in case themagnetic head slider 1 contacts the magnetic disk 10, the contact occursat the first surface constituting element 5 a. Friction force is exertedto the contacting surface. The depth d1 from the first surfaceconstituting element 5 a to the second surface constituting element 6 ais 30 nm and the depth d1 can limit the contacting surface between themagnetic head slider 1 and the magnetic disk 10 to the first surfaceconstituting element 5 a.

[0052] Mounting the magnetic head 9 on the first surface constitutingelement 5 a, the magnetic head 9 approaches the magnetic disk 10 to theclosest and the recording density can be improved.

[0053] The third surface constituting elements 7 a and 7 b arestructured surrounding the second surface constituting elements 6 a, 6 band 6 c.

[0054] The airflow, having entered between the magnetic head slider 1and the magnetic disk 10, is compressed by the third surfaceconstituting elements 7 a and 7 b, and then enters the second surfaceconstituting elements 6 a, 6 b and 6 c.

[0055] The third surface constituting elements 7 a and 7 b correspondsto the step air bearing surface or the tapered surface of the magnetichead that has been widely used.

[0056] The depth d2 from the second surface constituting element to thethird surface constituting element is very important parameter toequalize the flying height over the all surface of the magnetic disk.This will be described afterward.

[0057] The fourth surface constituting element 8 is surrounded by thethird surface constituting element 7 b and sub-ambient pressure force isgenerated at the fourth surface constituting element 8 (this sub-ambientpressure force exerts the slider to approach the magnetic disk).

[0058] That is, the fourth surface constituting element 8 corresponds tothe recess for generating sub-ambient pressure force of the conventionalmagnetic head that has been widely used.

[0059] The depth d3 from the third surface constituting element 7 a tothe fourth surface constituting element 8 is very important to reducethe decrease of flying height caused by the atmospheric pressure drop inthe high altitude and this will be described afterward.

[0060]FIG. 4 shows the relation between the friction force actingbetween the first surface constituting element 5 a of the magnetic headslider 1 and the magnetic disk 10, and the vibration displacement (FIG.3, in the direction of arrow B) of the magnetic head slider 1 in thefirst preferred embodiment of the present invention.

[0061] The friction force is measured by a friction sensor comprising apair of parallel leaf springs and a strain gauge.

[0062] For measuring the friction force with the actual magnetic diskdevice, for example, the friction force can be obtained indirectly bymeasuring the rotational torque of a spindle motor.

[0063] For measuring the vibration displacement of the magnetic headslider 1, the velocity variation of the magnetic head slider 1 caused bythe contact in the direction of the arrow B is measured by a laserdoppler vibrometer.

[0064] The laser doppler vibrometer, model OFV2700 made by Polytec PIInc. was used with the sampling frequency of 4 MHz.

[0065] To remove the influence of the run-out frequency of the magneticdisk and the resonant frequency of the suspension, we treat high-passfiltering process of 40 KHz to the data measured by the laser dopplervibrometer.

[0066] After the above data processing, the vibration displacementwaveform is obtained by integrating the velocity data with time.

[0067] The vibration amplitude shown by FIG. 4 indicates the value ofthe standard deviation of the vibration displacement waveform after theabove signal processing.

[0068] For measuring the vibration displacement by contact with theactual magnetic disk device, for example, there is a method of measuringit from the read waveform of the magnetic head 9.

[0069] When the vibration displacement is larger, jitter that isaffected by the vibration in the direction of bits (peripheraldirection) and off-track affected by the vibration in the direction ofthe track width will become more conspicuous, and the bit error rate ofthe magnetic disk device will be higher as the result of it.

[0070] As is shown by FIG. 4, when the friction force is zero, that isthe magnetic head slider 1 is floating on the magnetic disk 10 and doesnot contact the magnetic disk, the vibration of small amplitude of 0.3nm is seen (at friction is zero on the axis of abscissa in FIG. 4).

[0071] When the flying height of the magnetic head 1 decreases furtherand the magnetic head 1 starts to touch the magnetic disk 10, thefriction force between them increases.

[0072] Corresponding to the increase of the friction force, thevibration amplitude increases gradually.

[0073] In case the friction force increases, if the moment by thefriction force around pivots (supporting points that support the slider)is smaller enough than the moment formed around the pivots by air forceformed between the magnetic head slider and the magnetic disk, themagnetic head slider runs in contact on the magnetic disk stably, theincrease of the vibration amplitude is smaller in spite of the contact,and according to the experimental result, the vibration amplitude isapproximately 1 nm when the friction force is not more than 10 mN.

[0074] In such a range where the friction force is not more than 10 mN,the similar bit error rate can be obtained to those with the floatingmagnetic head.

[0075] However, when the friction force exceed 10 mN, the moment aroundthe pivots by the friction force is equivalent to or more than themoment around the pivots by the air force, the vibration amplitudeincreases drastically.

[0076] In such a region of the friction force, the magnetic head 9cannot record or reproduce data on the magnetic disk 10 and the biterror rate increases suddenly.

[0077] With the preferred embodiment of the present invention, thefriction force at which the vibration amplitude increases suddenly was10 mN but this critical friction force is considered to depend on theshape of the magnetic head slider.

[0078] The magnetic head slider 1 of the preferred embodiment of thepresent invention has, as above described, the shallow depth 3 of thefourth surface constituting element 8 that generates the sub-ambientpressure force that is 900 nm, and therefore, the slider having thesizes of 1.25 mm in length, 1.0 mm in width and 0.3 mm in thicknessgenerates very large sub-ambient pressure force of 30 mN for its size.

[0079] Further, the magnetic head slider 1 contacts the magnetic disk 10with the first surface constituting element 5 a having small area andthe other second, third and fourth surfaces are separated far from themagnetic disk 10, and therefore, there is a merit that the contactingsurface is limited to the first surface constituting element 5 a.

[0080] The magnetic head slider 1 of the preferred embodiment of thepresent invention comprises the structure provided with theabove-described area (especially, the first surface constituting element5 a is set small) and the depth.

[0081] Considering these, when the different configuration of themagnetic head slider than the magnetic head slider 1 of the preferredembodiment of the present invention is used, the critical friction forceis thought to be less than 10 mN.

[0082] This means a stable contact area is narrow and it is notdesirable from the point of view of the reliability of the magnetic diskdevice.

[0083]FIG. 5 is a diagram showing the relation between the pitchattitude angle è and the vibration amplitude. The pitch attitude angleis obtained from the results of the flying height measurement. Theflying height is measured with a Dynamic Flying Height Tester made byPhase Mertrics, Inc.

[0084] The flying heights of the edge on the air flow-in side and theedge on the air flow-out side are measured using an ultra-smooth glassdisk having mean surface roughness Ra of 0.5 nm, and the pitch attitudeangle è is obtained by the difference of the flying heights and thedistance between both measuring points.

[0085] As is shown by FIG. 5, when the pitch attitude angle decreases tonot more than 50 micro-radian, the vibration amplitude abruptlyincreases.

[0086] This means that in case the magnetic head slider begins tocontact the magnetic disk at the edge on the air flow-in side, thevibration amplitude will increase abruptly.

[0087] Therefore, the pitch attitude angle must be at least 30micro-radian or more and it is preferable for the pitch attitude angleto be 50 micro-radian or more for the standpoint of reducing thevibration amplitude.

[0088] As above described, the configuration and pitch attitude angle ofthe magnetic head slider 1 affect the friction force, and therefore,affects the vibration amplitude strongly.

[0089] Similarly, the surface roughness and the form of the magneticdisk 10 is measured with the scanning probe microscope of DigitalInstruments, Inc. Measuring area was 20

m×20

m. Measuring resolution in the direction of height was 0.02 nm.

[0090] Measured data was flattening treated by a two-stage filter beforethe analysis.

[0091] As an index of surface roughness, adding to a generally usedcentral surface roughness (mean surface roughness) Ra and maximum heightRp, peak counts are acquired simultaneously as the peak counts are foundto affect substantially to the vibration amplitude.

[0092] The peak count is defined as the count of peaks exceeding athreshold level that is 1 nm above the centerline of the surfaceroughness (mean surface roughness plane).

[0093] (The peaks of the surface roughness exceeding the height of 1 nmfrom the mean surface roughness plane are counted).

[0094] The each of the magnetic disks used for the experiments this timeis a smooth disk having the mean surface roughness Ra of 1.5 nm and theglide height of 6 nm.

[0095] The method of obtaining the glide height is as follows.

[0096] The flying height of the slider is measured beforehand as thefunction of velocity using a special slider provided with an AcousticEmission (AE) sensor.

[0097] On the magnetic disk to measure the glide height, the slider isfloated.

[0098] From the velocity, where the output of the AE sensor increases bythe contact between the slider and the magnetic disk when the flyingheight is reduced by decreasing velocity gradually, the glide height canbe defined by an inverse operation (a flying height acquired from thefunction between the flying height and the velocity).

[0099] There is a strong correlation among the mean surface roughnessRa, the maximum surface roughness height Rp and the glide height, and itis widely known that to decrease the glide height, the surface roughnessmust be reduced.

[0100] However, when the surface roughness is lower, the contactingsurface area is larger at the contact between the magnetic head sliderand the magnetic disk, and the friction force will increase resulting inthe increase of the vibration amplitude.

[0101] This will adversely affects the reliability of the magnetic diskdevice profoundly.

[0102] To reduce the frequency of contact, the decrease of the glideheight by smoothing the surface roughness will be effective, but thesmoother surface will cause large vibrations when the contact happensand therefore, there is a contradictory request that surface roughnessis not to be smoother.

[0103] This time, the inventors found that the difference of peakcounts, that are the index of microscopic form of the surface of themagnetic disk, strongly affects the vibration amplitude at the contactwith similar glide height as is described below.

[0104]FIG. 6 is a diagram showing the relation between the peak count,that is the index that shows the surface form of the magnetic disk 10,and the vibration amplitude.

[0105] Disks shown in FIG. 6 are with the glide height of 6 nm. The peakcounts varied from 250/400

m2 to 1600/400

m2.

[0106] As is shown by FIG. 6, the fewer the peak counts, the larger thevibration amplitude.

[0107] On the other hand, the vibration amplitude decreases with thepeak count of 700 or more.

[0108] When the peak count is fewer, the peak of the surface roughnessis pushed down elastically by the contact force exerted at the contactand the magnetic head slider contacts the magnetic disk surface at themean plane of the surface roughness.

[0109] Therefore, it is considered that the vibration amplitudeincreases with the larger friction force by the larger contactingsurface.

[0110] When the peak count exceeds a certain point, the many peaks ofthe surface roughness will share the contacting force, the deformationof the peaks of the surface roughness will be smaller and the increaseof the contacting surface area will be prevented.

[0111] Therefore, the friction force and the vibration amplitude aresmaller.

[0112] Though it could not be confirmed in the extent of the experimentthis time, but it is predicted that the excessive peak count willincrease the contacting area excessively and will increase the vibrationamplitude.

[0113] As above described, the magnetic disk, used with the low flyingheight of the magnetic head slider that requires the consideration ofthe contact between the magnetic head slider and the magnetic disk,requires the consideration of peak counts adding to the reduction ofconventional surface roughness index Ra and Rp for reducing the glideheight.

[0114] In the preferred embodiment of the present invention, the peakcount of 700/400

m2 or more is desirable for reducing the vibration amplitude.

[0115]FIG. 7 is the profile (calculated value) of the flying height ofthe magnetic head slider 1 over the whole surface of the magnetic diskat the ground altitude and the high altitude.

[0116] The calculation is with the condition of the magnetic disk withthe diameter of 65 mm (generally called 2.5 inch) and the spindlerotational speed of 4200 rpm.

[0117] The average flying height at the ground altitude is approximately10 nm and uniform floating profile is realized over the whole surface ofthe magnetic disk (mainly by the effect of the depth d2 shown by FIG.2).

[0118] The decrease of the flying height at the high altitude is 2 nm atthe inner circumference of the magnetic disk and 1 nm at the outercircumference, and excellent floating profile is realized at the highaltitude.

[0119] In this example of calculation, the average flying height isassumed to be 10 nm, but the measured flying height of the mass-producedmagnetic head slider varies caused by the variation of themanufacturing.

[0120] With the magnetic head slider of the preferred embodiment of thepresent invention, the variation of the flying height of ±2 nm and thedecrease of the flying height of 1 nm of the magnetic head slider atseek operation are anticipated.

[0121] Assuming the use of the smooth disk of the glide height of 6 nm,the magnetic head slider of the preferred embodiment of the presentinvention is assumed to contact the magnetic disk at the worst conditionat the high altitude.

[0122] The magnetic head slider of the preferred embodiment of thepresent invention is designed, as described later, to minimize the dropof the flying height at the high altitude.

[0123] As described above, sub-ambient pressure force is large so thatthe variation of the flying height by the variation of the manufacturingis smaller than those of the conventional cases.

[0124] Therefore, in general, when the average flying height at theground altitude is 15 nm or less, the contact between the magnetic headslider and the magnetic disk must be considered at the worst condition.

[0125]FIG. 8 is a diagram showing the relation between the depth d1between the first surface and the second surface of the magnetic headslider 1 and the vibration amplitude.

[0126] The area of the first surface is very small so that it does notaffect much to the floating force of the magnetic head slider.

[0127] However, when the depth d1 is extremely shallow as 10 nm or less,the possibility of contacting up to the constituting surface 6 a of thesecond surface increases at the contact between the magnetic head slider1 and the magnetic disk 10.

[0128] Therefore, the depth d1 is preferred to be 10 nm or more.

[0129] In reverse, when the d1 is too deep, the surface 2 that is theactual rail surface is separated from the surface of the magnetic disk,and the sub-ambient pressure force is diminished causing undesirablecondition at the variation of the manufacturing and at the contact atthe standpoint of stability.

[0130] The d1 is desirable to be in the range of 10 nm to 50 nm.

[0131]FIG. 9 is a diagram showing the relation between the depth d2between the second surface and the third surface of the magnetic headslider 1 and the ratio of the maximum and minimum flying height of thefloating profile over the whole surface of the magnetic disk. Assumedcondition is similar to that of FIG. 7.

[0132] As described above, the depth of d2 strongly affects to theuniformity of the floating profile. In an actual case, when d2 is 200 nmor more, the floating ratio exceeds 1.2 and the uniform floating profilecannot be kept anymore.

[0133] On the other hand, when d2 is extremely shallow, the floatingprofile will be uniform but the deviation of the flying height by thevariation of the depth value of d2 will increase.

[0134] Therefore, in the preferred embodiment of the present invention,the depth d2 of 50 nm to 200 nm is preferable from the viewpoint ofequalizing the floating profile and decreasing the fluctuation of theflying height.

[0135] The adequate depth of d2 for equalizing the floating profiledepends on the condition of the magnetic disk device.

[0136] For example, in case of the magnetic disk device having a 95 mmdiameter (generally called a 3.5 inch) magnetic disk of which spindlerotational speed is 7200 rpm, the optimum depth of d2 is 150 nm to 400nm.

[0137]FIG. 10 is a diagram showing the relation between the depth d3between the third surface and the fourth surface, and the decrease ofthe flying height at the high altitude from the flying height at theground altitude.

[0138] Generally, the decrease of the flying height at the high altitudeis more conspicuous at the inner circumference of the magnetic disk, sothat the decrease of the flying height is measured at the innercircumference.

[0139] Assumed condition is similar with that of FIG. 7.

[0140]FIG. 10 shows that the decrease of the flying height is minimum atthe depth d3 of 800 nm.

[0141] When d3 is larger or smaller than the value, which gives theminimum decrease of the flying height, the decrease of the flying heightis larger.

[0142] In the condition of the magnetic disk device of the preferredembodiment of the present invention, the depth d3 of 400 nm to 1.3

m is preferable.

[0143] In other words, the position of the magnetic head slider againstthe magnetic disk referring to FIG. 3 is held at a certain flying heightof the slider by balancing between the sum of the slider suspension loadW and the sub-ambient pressure force N exerted to the fourth surfacehaving the depth d3, and the positive pressure P exerted to the slider.

[0144] If the sub-ambient pressure force does not change at the highaltitude from that of the ground altitude in spite of the decrease ofthe positive pressure P at the high altitude, the flying height of theslider drops proportionally to the decrease of the positive pressure,but actually the sub-ambient pressure force drops at the high altitude,and if the level of the drop of the sub-ambient pressure force issimilar to the level of the drop of the positive pressure, the similarfloating relations is maintained both in high altitude and in groundaltitude.

[0145] The depth d3, which maximize the drop of the sub-ambient pressureforce to the level of the drop of the positive pressure, is 800 nm.

[0146] That is, it has the characteristic of changing the sub-ambientpressure force by the value of the depth d3.

[0147] The optimum depth of d3, which reduces the drop of the flyingheight at the high altitude depends on the unit condition.

[0148] For example, in case of the magnetic disk device having a 95 mmdiameter magnetic disk, of which spindle rotational speed is 7200 rpm,adequate depth of d3 is 1 μm to 2.5 μm.

[0149]FIG. 11 is a diagram showing the relation between the area of thefirst surface constituting element 5 a of the magnetic head slider 1 andthe vibration amplitude.

[0150] It shows that the vibration amplitude increases unilaterally withthe increase of the area of the first surface constituting element 5 a.

[0151] Therefore, the area of the first surface constituting element 5a, which is the contacting surface with the magnetic disk, must be assmall as possible.

[0152] For example, to limit the vibration amplitude to 1

m or less, the area of the first surface constituting element 5 a isdesirable to be 1000

m2 or less.

[0153] In the preferred embodiment of the present invention, themagnetic head slider comprises substantially parallel four surfaces andwhen the surfaces are sequentially named from the surface nearest to themagnetic disk as a first surface, a second surface, a third surface andfourth surface in a state the magnetic head slider faces the magneticdisk, the magnetic head slider is constituted in such a way thatS1>S2>S3>S4, while the total area of the magnetic head slider existinginside the first surface is S1, the total area of the magnetic headslider existing inside the second surface is S2, the total area of themagnetic head slider existing inside the third surface is S3 and thetotal area of the magnetic head slider existing inside the fourthsurface is S4.

[0154]FIG. 12 shows an example of the process of producing the magnetichead slider of the present invention. Currently, as the base material ofthe magnetic head slider, sintered material of such as, AlTiC isgenerally used.

[0155] As a surface finally facing the magnetic disk, a carbonprotecting film layer 12 for the main purpose of preventing thecorrosion of magnetic head 9 is formed on a silicon layer 11, which isan adhesive layer.

[0156] In the preferred embodiment of the present invention, the desiredshape is formed by repeating Ar ion milling for three times as is shownby FIG. 12.

[0157] At the final step, the silicon adhesive layer 11 and the carbonprotective layer 12 remain only on the first surface constitutingelement 5 a, which is mounted with the magnetic head, and on the firstsurface constituting elements 5 b and 5 c.

[0158] In the preferred embodiment of the present invention, the Ar ionmilling is used as the method of processing, but the essential part ofthe present invention is not the method of processing and therefore, theshape can be formed with any kinds of processing method.

[0159]FIG. 13 is a top view of the magnetic head slider of the secondpreferred embodiment of the present invention, and FIG. 14 is a A-Across section viewed in the direction of arrows in FIG. 13.

[0160] The difference of the magnetic head slider 1 of the secondpreferred embodiment of the present invention from the magnetic headslider of the first preferred embodiment of the present invention isthat the flow-in edge side of the first surface constituting element 5 aand the flow-out edge side of the first surface constituting elements 5b and 5 c are at the same depth with the fourth surface constitutingelement 8.

[0161] By this preferred embodiment of the present invention, as thereis not the third surface constituting element 7 a which is connected tothe first surface constituting element 5 a, the floating force generatedby the first surface constituting element 5 a can be decreased more thanthat of the first preferred embodiment of the present invention.

[0162]FIG. 15 is a top view of the magnetic head slider of the thirdpreferred embodiment of the present invention.

[0163] The first surface constituting element 5 a and the second surfaceconstituting element 6 a of the magnetic head slider of the thirdpreferred embodiment of the present invention are not separated by thethird surface constituting element 7 a but formed continuously. The areaof the first surface constituting element 5 a is made smaller to theextent the size of the magnetic head 9 allows.

[0164]FIG. 16 is a top view of the magnetic head slider of the fourthpreferred embodiment of the present invention.

[0165] Similarly to the third preferred embodiment of the presentinvention, the size of the first surface constituting element 5 a ismade as small as possible, and the third surface constituting element 7a separates between the first surface constituting element 5 a and thesecond surface constituting element 6 a.

[0166]FIG. 17 is a top view of the magnetic head slider of the fifthpreferred embodiment of the present invention. The shape of the magnetichead slider of the fifth preferred embodiment of the present inventionis similar to that of the first preferred embodiment of the presentinvention but removed with the first surface constituting elements 5 band 5 c positioned on the side of air flows in.

[0167] While the magnetic head and the magnetic disk perform therecording and the reproduction in contact, the first surfaceconstituting elements 5 b and 5 c are floating apart on the magnetichead and these surfaces are not related to the essence of the presentinvention.

[0168]FIG. 18 is a figure of the magnetic disk device 13 mounted withthe magnetic head slider, which are disclosed by the first to fifthpreferred embodiment of the present invention.

[0169] This magnetic disk device is provided with a load/unloadmechanism and the magnetic head slider 1 stands by on a ramp 14 whilethe magnetic disk device is stopped.

[0170] Only while the magnetic disk device is in operation, the magnetichead slider is loaded on the magnetic disk 10 and the recording or thereproduction is executed.

[0171] Using the magnetic head slider of this preferred embodiment ofthe present invention, the vibration of the magnetic head slider is notamplified by the contact with the magnetic disk while the recording orthe reproduction, and stable recording or reproduction can be continuedfor a long time.

[0172]FIG. 19 is a top view of the magnetic head slider of the sixthpreferred embodiment of the present invention.

[0173] The floating surface of the magnetic head slider of the first tofifth preferred embodiment of the present invention comprisessubstantially parallel four surfaces but the floating surface of themagnetic head slider of the sixth preferred embodiment of the presentinvention comprises substantially parallel three surfaces.

[0174] That is, the magnetic head slider comprises 6 a, 6 b and 6 cwhich are rail surfaces, 7 a and 7 b which are step air bearingsurfaces, and 8 which is a recess for generating sub-ambient pressureforce.

[0175] The feature of the sixth preferred embodiment of the presentinvention is that the rail surface 6 a is formed T shape by thecombination of a long sideway rail part 15 which is long in thecrosswise direction of the slider and a lengthwise rail part 16 which islong in the direction of the length.

[0176] By such configuration, the long sideway rail part 15, beingformed continuously from the step air bearing 7 a, generates floatingforce and floats on the magnetic disk 10.

[0177] On the other hand, as the lengthwise rail part 16 is narrow andcannot generate enough floating force, the flow-out edge and vicinity ofthe lengthwise rail part mounted with the magnetic head 9 contacts themagnetic disk.

[0178] Furthermore, the area of the lengthwise rail part is narrow sothat the vibration amplitude at the contact with the magnetic disk canbe kept smaller.

[0179] The contacting part of the magnetic head slider of this preferredembodiment of the present invention is not separated three dimensionallycompared with those of the first to fifth preferred embodiment of thepresent invention, and if the vibration amplitude is happened to beenlarged, there is a possibility the danger of contacting the longsideways rail part 15 with the magnetic disk.

[0180] However, there is a merit that the ion milling steps can be savedby one step compared to those of the first to second preferredembodiment of the present invention as the long sideways rail part 15and the lengthwise rail part 16 are on a same plane.

[0181] The center rail shape of the magnetic head slider of the sixthpreferred embodiment of the present invention can be formed by not onlythe ion milling process but by the Focus Ion Beam (FIB) process.

[0182] The FIB process is frequently used for forming the track width ofthe magnetic head in high precision.

[0183] The lengthwise rail part 16 of the sixth preferred embodiment ofthe present invention can also be formed by forming the flow-out edgeside of the rail surface 6 a at the forming of the track width.

[0184] In this case, a step difference, of which depth is different fromthat of the step air bearing 7 a formed by the ion milling, is formedaround the lengthwise rail part 16.

[0185]FIG. 20 is a top view of the magnetic head slider of the seventhpreferred embodiment of the present invention.

[0186] The floating surface 4 of the magnetic head slider of the seventhpreferred embodiment of the present invention comprises threesubstantially parallel surfaces similarly to that of the sixth preferredembodiment of the present invention.

[0187] However, different from the case with the sixth preferredembodiment of the present invention, the step air bearing 7 a separatesbetween the long sideways rail part 15 and a contact pad 17.

[0188] Both with the sixth and seventh preferred embodiment of thepresent invention, it is important for decreasing the vibrationamplitude that the area of the rail part near the element partcontacting with the magnetic disk comprising the lengthwise rail part 16and the contact pad 17 is narrower than the area of the long sidewaysrail part 15 which generates the floating force.

[0189] As described above, the present invention have the effect ofmaintaining high reliability by equalizing the flying height over thewhole surface of the magnetic disk and reducing the change of the flyingheight by the variation of processing, seek operation and operation atthe high altitude, and having the magnetic head slide on the surface ofthe magnetic disk smoothly at the contact between the magnetic head andthe magnetic disk.

What is claimed is:
 1. A magnetic head slider comprising: a firstsurface, a second surface, a third surface and a fourth surface whichare formed sequentially from a adjacent side to a magnetic disk, and agap of a magnetic head arranged on said first surface, wherein therelation of d1<d2<d3 is established where said d1 is a depth from saidfirst surface to said second surface, said d2 is a depth from saidsecond surface to said third surface, and said d3 is a depth from saidthird surface to said fourth surface.
 2. A magnetic head slider asclaimed in claim 1 , wherein said d1 is 10 nm to 50 nm, said d2 is 50 nmto 200 nm, and said d3 is 400 nm to 1.3

m.
 3. A magnetic head slider as claimed in claim 1 , wherein total areaof said first surface is smaller than total area of other said surfaces.4. A magnetic head slider as claimed in claim 1 , wherein the relationof S1<S2<S3<S4 is established where total area of said first surface issaid S1, total area of said second surface is said S2, total area ofsaid third surface is said S3, and total area of said fourth surface issaid S4.
 5. A magnetic head slider as claimed in claim 1 , wherein saidfirst surface is formed with a protective coat made of a carbon film. 6.A magnetic head slider as claimed in claim 1 , wherein said firstsurface is surrounded by said fourth surface.
 7. A magnetic head slidercomprising: a magnetic head mounting surface, which is mounted with amagnetic head, approaches a magnetic disk in operation, and of whicharea on a side of air flow-out edge is 1000

m² or less, a slider rail surface, which is separated from magnetic headmounting surface, formed with both surfaces adjacent to the air flow-inside and surface near the air flow-in edge, and has the depth of 10 nmto 50 nm from said magnetic head mounting surface, a slider step airbearing which is formed surrounding said slider rail surface and has apredetermined depth from said slider step air bearing surface, and arecess for generating sub-ambient pressure force which surrounds saidslider step air bearing surface.
 8. A magnetic head slider as claimed inclaim 7 , wherein said slider step air bearing surface has the depth of50 nm to 200 nm from said slider rail surface.
 9. A magnetic head slideras claimed in claim 7 , wherein said recess for generating sub-ambientpressure force surrounds said slider step air bearing surface, has thedepth of 400 nm to 1.3

m from said slider step air bearing surface.
 10. A magnetic head slideras claimed in claim 7 , wherein said slider step air bearing surface,which has the depth of 50 nm to 200 nm from said slider rail surface,and said recess for generating sub-ambient pressure force has the depthof 400 nm to 1.3

m from said slider step air bearing surface.
 11. A magnetic head slideras claimed in claim 7 , wherein said slider rail surface comprises along sideways rail surface on the air flow-in side and a lengthwise railsurface on the air flow-out side having said magnetic head, and area ofsaid long sideways rail surface is larger than area of said lengthwiserail surface.
 12. A magnetic head slider as claimed in claim 11 ,wherein a different surface separates between said long sideways railsurface and said lengthwise rail surface.
 13. A magnetic head slider asclaimed in claim 7 , wherein said slider rail surface has T formstructure comprising the long sideways rail surface on the air flow-inside and the lengthwise rail surface on the air flow-out side, and saidmagnetic head is mounted on the air flow-out edge of said lengthwiserail surface, the area of which is smaller than the area of said longsideways rail surface.
 14. A magnetic head slider comprising: pluralityof surfaces which are formed sequentially from a adjacent side to amagnetic disk, and a said slider rail surface, which is arranged in nearair flow-out edge on nearest surface of said plurality of surfacescomprising a long sideways rail surface on the air flow-in side and alengthwise rail surface on the air flow-out side, has a magnetic head,wherein an area of said long sideways rail surface is larger than anarea of said lengthwise rail surface.
 15. A magnetic head slider asclaimed in claim 14 , wherein a different surface separates between saidlong sideways rail surface and said lengthwise rail surface.
 16. Amagnetic disk device comprising: a magnetic head slider mounted with amagnetic head which size is 1.25 mm or less in length, 1 mm or less inwidth and 0.3 mm or less in thickness, and a magnetic disk of whichsurface roughness Ra is 2 nm or less and the friction force exerted withsaid magnetic head slider in operation is 10 mN or less.
 17. A magneticdisk device as claimed in claim 16 , wherein the peak count of saidmagnetic disk is 700/400

m² or more.
 18. A magnetic disk device of the claim 16 , wherein saidmagnetic head slider has the floating pitch attitude angle of 50micro-radian or more against said magnetic disk.